IC manufacturers typically use Automated Test Equipment (ATE) systems to test their ICs before shipping to customers. Such ATE systems typically include an IC tester and an IC device handler. A device tester is an expensive piece of computing equipment that transmits test signals via tester probes to an interface structure. The interface structure transmits signals between the leads of an IC under test and the device tester. The device handler is an expensive precise robot for automatically moving ICs from a first storage area to the interface structure, sometimes by way of a preparation station where the ICs are heated or cooled before testing, and then from the interface structure to a second storage area. Such ATE systems are well known and take many forms.
FIG. 1 is a perspective view showing a simplified device handler 100, which is exemplary of the type of device handlers often utilized by IC manufacturers to facilitate high speed testing of their IC products. Device handler 100 is constructed in a box-shaped housing having two long vertical sides 101 and 103 (e.g., eight feet wide by six feet high), and two short vertical sides 105 and 107 (e.g., four feet wide by six feet high). Device handler 110 includes a control section 110, which is described below with reference to FIG. 2, and an operation section 120. In general, operation section 120 includes one or more robots (mechanisms) 121 that are operated using instruction signals generated by control section 110 to move ICs between various test/storage stations. For example, robot 121 may be programmed to move ICs from a first storage location 122 to a pre-heating station 123, to move heated ICs from preheating station 123 to a tester interface station 124 for testing, and from tester interface station 124 to a second storage location 125. Note that the depiction of robot 121 in FIG. 1 is greatly simplified for illustrative purposes, and that the actual mechanism used to move the ICs to the various stations of operation section 120 includes several separately movable motors and actuators that are mounted on a lower portion 126 and an upper portion 127 (which is shown in dashed lines for illustrative purposes).
FIG. 2 is a front elevation view showing front side 105 of device handler 100, and shows control section 110 in additional detail. Control section 110 provides a technician (user) interface station for purposes of programming a control unit 210, which in turn transmits control signals to robot 121 (FIG. 1) and other mechanisms of device handler 100. In particular, control unit 210 includes user-programmable electronic circuitry (i.e., a computer) that selectively transmits control signals to the servo motors of robot 121, thereby causing robot 121 to perform the various handler functions described above in a predefined sequence. The faceplate of control unit 210 includes a display 212 and a control panel 214. One or more input devices, such as a keyboard 216 and/or a mouse/trackball 218, are connected directly to control unit 210, for entering user-defined program instructions. Display 212 displays information associated with the programming and operation of device handler 100, including operating conditions and program instructions. Control panel 214 includes several switches and indicator lights that facilitate further control of control unit 210. For example, the operating mode (OP MODE) of control unit 210 is controlled by a teaching (TEACH) mode push-button switch 221 and a production (PROD) mode push-button switch 222. In addition, several switches and indicator lights are provided on control panel 214 that initiate and indicate the control state of control unit 210. For example, a “start” (run) control state is initiated by pressing a START push-button switch 223, and the start/run control state is indicated by lighting an associated indicator lamp 224. Similarly, a “pause” control state is initiated by pressing a PAUSE push-button switch 225, and the “pause” control state is indicated by lighting an associated indicator lamp 226. Control panel also includes an Emergency Machine Off (EMO) control section that includes an EMO push-button switch 227, whose function is described in additional detail below.
The operation of device handler 100 will now be described with reference to FIGS. 1 and 2. In general, the operation of device handler 100 requires an initial calibration (“teach”) phase that is initiated, for example by pressing teaching mode push-button switch 221 (FIG. 2). During the teach phase robot 121 is calibrated, for example, to identify fixed reference positions for purposes of orientating a pickup arm of robot 121. After calibration, device handler 100 is switched into the production mode to perform testing operations. Typically, a test operation is initiated by entering an associated program into control unit 210, loading ICs into first storage location 122 (FIG. 1), pressing production mode push-button switch 222 (FIG. 2), and then pressing start/run push-button switch 223. Of course, those of ordinary skill in the art will understand that initiating a test operation is rarely this easy, and that a certain amount of fine tuning is required to maintain full scale testing operations by device handler 100. This fine tuning is typically performed while device handler 100 is in the production operating mode. When an error or misalignment of robot 121 is detected, pause push-button switch 225 is pressed to initiate a controlled stoppage of robot 121, a correction is performed (e.g., a code line of the program is changed to correct the error or misalignment, a robot portion is realigned, a temperature setting is changed, or a loose screw is retightened), and then the program is resumed by pressing run push-button switch 223.
A problem associated with conventional device handlers is that robot 121 and its associated mechanisms present very dangerous moving structures that can injure or maim a technician who accidentally places an arm or hand into operating section 120 while robot 121 is in operation. In particular, during both teaching mode and production mode operations, a technician is typically required to perform manual adjustments and maintenance activity that involve inserting his/her hands and arms into operating section 120. Normal safety procedures typically dictate that these adjustments take place only when, for example, a pause control state is initiated and all activity of robot 121 has terminated. However, conventional device handlers, such as the Seiko-Epson HM-3000 and HM-3500 Robotive IC Handler, produced by Seiko Epson of Tokyo, Japan, have been produced without sensors that are capable of detecting the presence of a technician's hands/arms in the operating section, and therefore cannot prevent such injuries from occurring when normal safety procedures are not followed. In the event of these injuries, the only “safety” mechanism available on conventional device handlers is EMO push-button switch 227, which, when pressed, immediately terminates the power supplied to robot 121. Unfortunately, this “safety” mechanism is not designed to prevent injury, only to react to ongoing emergencies.
What is needed is a safety system that allows a technician to safely access the operating section of an IC device handler without risk of injury due to unanticipated operation of the handler's robot mechanism. In particular, what is needed is a safety system that is capable of sensing the presence of a technician's hands/arms in the operating section, and detecting the operating mode and/or control state of the IC device handler, and that can only be muted (disabled) when there is no danger of robot mechanism movement. What is also needed is a method for retrofitting existing IC device handlers with a safety system having these features that is both reliable and cost efficient.